The appearance of what we typically think of as attractive, natural-looking skin is influenced by a number of factors. It is generally accepted that a "standard" beautiful skin has a transparent quality about it, with uniform undertones of color. The basis for what we regard as this natural appearance lies in the skin structure itself. The outer layer of human skin is a semi-transparent layer known as the stratum corneum. The transparency of the stratum corneum permits glimpses of the deeper layers of skin, where blood vessels and pigments reside; the reddish hue of the blood vessels' hemoglobin, with the brown/black hue of melanin, the primary skin pigment, combine to produce what we view as the skin's color. Of course, in addition to ideal skin having the transparent look with a uniform color distribution, it should also be smooth and even, with no apparent surface flaws. Needless to say, few individuals can ever hope to meet such a standard without some outside assistance. Thus, a wide variety of cosmetics exist to help out where nature has failed.
In ancient times, although makeup was worn on facial skin, it was seldom intended to mimic the actual appearance of natural, but perfect, skin; in many cases, it was frankly and intentionally artificial-looking. In recent times, however, the trend has been toward more natural-looking makeups. In particular, one of the long-sought goals has been the development of a foundation that does not give the user a "made-up" look. In reality, however, it is difficult to accomplish the goal of achieving coverage of flaws and unevenness of skin tone, while still maintaining the vibrant look of clean bare skin. This is primarily because those components of makeups which provide the desired color and coverage, such as the titanium or iron oxide pigments, are largely opaque, and therefore obscure that sought-after vibrant transparency. Although in recent years, transparent pigments have become available, the coverage needed to mask flaws in the surface of the skin is frequently lacking.
Clearly, there are competing goals in the development of a natural-looking makeup which, given currently available technology, seem difficult, if not impossible to resolve. Very recently, the cosmetics industry has turned to a detailed study of the optics of light absorption, reflection and scattering in the skin in an attempt to design a product which, when applied to the skin, will convey to the viewer the impression of a natural but flawless clean skin (See, for example, Nishikata et al., Cosmetics and Toiletries 112: 39-55, 1997). It has, for example, been recognized that the angle of viewing of the skin will alter the appearance to the viewer: the viewer will see more of the red of hemoglobin in the skin's dermis when the skin is viewed at close to a perpendicular angle, while brown, due to the melanin content of the outer layers of epidermis, will predominate when the skin is viewed at a shallower angle. Although strides have been made in the understanding of the optical events leading to our perception of natural-looking skin, the development of products based on this knowledge has not to date been fully realized. However, the present invention represents a substantial advance in the preparation of a cosmetic which conveys the transparency and color of natural skin, while providing considerable masking of surface flaws.